xz: Fix "xz --list --robot missing_or_bad_file.xz".

It ended up printing an uninitialized char-array when trying to
print the check names (column 7) on the "totals" line.

This also changes the column 12 (minimum xz version) to
50000002 (xz 5.0.0) instead of 0 when there are no valid
input files.

Thanks to kidmin for the bug report.
1 file changed